If you say that someone has stacks of something, you mean that they have a lot of it.
堆 • If the job's that good, you'll have stacks of money. 如果那份工作真那么好,你就会有成堆的钱。
If you stack a number of things, you arrange them in neat piles.
堆放; 摞起 • Mrs. Cathiard was stacking the clean bottles in crates. 卡提亚夫人当时正在把干净的瓶子堆放到板条箱里。